Wednesday, September 24, 2014

EMF & Health (effect & radio frequency)

The published results available in 2005 were insufficient to draw firm
conclusions concerning the possible non-thermal effects of radiofrequency
fields on the blood-brain barrier (BBB). This critical review deals with 16
articles on this topic published since 2005. The methodological quality of
these articles was not equivalent. We therefore analysed the underlying
methodologies from both their biological and physical aspects. We conclude that
recent studies provide no convincing proof of deleterious effects of RF on the
integrity of the BBB, for specific absorption rates (SAR) up to 6 W/kg.

Summary

This summary of effects on the BBB is based on 16 research articles, including:
• Three studies in vitro:
Two of these studies [8,9] showed no effect of semi-chronic exposure to GSM or
UMTS electromagnetic radiation for SAR values from 0.02 to 1.64 W/kg with
validated dosimetry, but with incomplete dosimetry in one case. The third study
[10] reported effects of RF at 915 MHz with modulation and an unusual exposure
system, but without dosimetry to determine the SAR.
• Two studies in humans:
Two studies have reported weak variation of circulating protein concentrations
in humans, but the methodologies of these methods include several major flaws,
particularly as concerns the choice of parameter, making it impossible to
interpretate the results. Indeed, the parameter used has not been validated,
varies between individuals and is determined in the blood rather than in the
CSF [22,23].
• Eleven studies in vivo:
Effects of exposure to RF on the permeability of the BBB and/or neuronal
integrity have been sought in vivo, in conditions of acute, semi-chronic or
chronic exposure, with a large range of SAR, extending from 0.0018 to 20 W/kg
for GSM 900 or TDMA at 1439 MHz or 2450 MHz (continuous and modulated) signals.

This paper summarizes the weight of scientific evidence on whether or not
exposure of laboratory animals to radiofrequency (RF) energy a) causes or
promotes tumor development and b) affects the integrity of the blood-brain
barrier (BBB). Forty-four studies of tumorigenesis were identified. In addition
to the studies of spontaneous tumorigenesis in animals exposed to RF energy
alone, 21 of the 44 studies investigated tumor promotion in animals exposed to
RF energy in combination with chemicals [e.g., ethylnitrosurea (ENU) and 7,12-dimethylbenz[a]anthracene
(DMBA)] and physical agents (e.g., x-rays and ultraviolet radiation) known to
cause cancer. Evaluation of the results in all 44 studies on tumorigenesis
showed no adverse effect of RF exposure up to two years in duration at dose
rates up to 4 W/kg (10 times greater than the occupational safety limit) on
carcinogenic processes (initiation, promotion and co-promotion). Other
information in these studies on survival and body mass provides supporting
evidence for the conclusion that RF exposure does not affect tumor development
because a) 26 of 27 studies since 1983 reported no significant change on
survival and b) all 27 studies reporting body mass observed no significant
change in this health indicator. The weight of evidence of 44 animal
tumorigenic studies supports the conclusion that RF exposure within current
internationally accepted limits, when given alone or in combination with
carcinogens, is unlikely to affect tumor development in human beings.
Furthermore, the results showing a lack of RF effects on tumorigenesis,
survival and body mass in live animals offer a strong challenge to studies
reporting potential genotoxic and other health effects based on research with
cells in culture and other biological samples exposed in vitro to RF energy.
Another area of research has focused on whether or not RF exposure could affect
the integrity of the blood-brain barrier (BBB) that protects the brain from
potentially to- - xic molecules in the blood. A number of laboratories have
confirmed that the permeability of the BBB can be affected if the temperature
of the brain is increased significantly. The effect is a temperature effect
because it does not matter whether the effect on the BBB was caused by exposing
the animal to heated air, heated water or RF energy. Reports in the 1970s and
more recent reports of changes in BBB permeability following exposure to levels
of RF energy that would not significantly increase the brain temperature have
failed the test of independent confirmation.

AIMS: To study the effect of long-term exposure to global system for mobile
communication (GSM) radiofrequency fields on vascular permeability in murine
brains.

METHODS: Using a purpose-designed exposure system at 900 MHz, mice were given a
60-minute far-field, whole body exposure on each of 5 days per week for 104
weeks at specific absorption rates (SAR) of 0.25, 1.0,2.0 and 4.0 W/kg. Control
mice were sham-exposed or permitted free movement in a cage to evaluate any
stress-related effects. Albumin immunohistochemistry was used to detect
increased vascular permeability and the efficacy of the vascular tracer was
confirmed with a positive control group exposed to a clostridial toxin known to
increase vascular permeability in the brain.

RESULTS: In all exposed and control groups, albumin extravasation was minimal,
often leptomeningeal, and was deemed insignificant as a maximum of three
capillaries or venules in a given brain showed leakage from the very many blood
vessels present in the three coronal brain sections.

CONCLUSIONS: These results suggest that prolonged exposure to mobile
telephone-type radiation produces negligible disruption to blood-brain barrier
integrity at the light microscope level using endogenous albumin as a vascular
tracer.

A total of 1170 rats comprised of 65 male and 65 female Han Wistar rats per
group were exposed for 2 h/day, 5 days/ week for up to 104 weeks to GSM or DCS
wireless communication signals at three nominal SARs of 0.44, 1.33 and 4.0
W/kg. A preliminary study confirmed that the highest exposure level was below
that which was capable of causing a measurable increase in the core temperature
of the rat. Additional groups for each modulation were sham exposed, and there
was also an unrestrained, unexposed (cage) control group. Fifteen male and 15
female rats per group were killed after 52 weeks. From the remaining 50 male
and 50 female rats per group, surviving animals were killed after 104 weeks.
Evaluations during the study included mortality rate, clinical signs, recording
of palpable masses, body weight, food consumption, ophthalmoscopic examination,
and clinical pathological investigations. Terminal investigations included
organ weight measurement and macroscopic and microscopic pathology
examinations. There was no adverse response to the wireless communication
signals. In particular, there were no significant differences in the incidence
of primary neoplasms, the number of rats with more than one primary neoplasm,
the multiplicity and latency of neoplasms, the number of rats with metastases,
and the number of benign and malignant neoplasms between the rats exposed to
wireless communication signals and rats that were sham exposed.